1. Field of Invention
The present invention relates to an ultrasonic sensor for detecting double sheets and a method of detecting double sheets using the same. More particularly, the present invention relates to an ultrasonic sensor for detecting double sheets and a method of detecting double sheets using the same, in which in configuring the ultrasonic sensor for detecting double sheets of banknotes passing through a transfer path, the ultrasonic sensor is configured to include an ultrasonic wave generator and an ultrasonic wave receiver provided in pair to face each other in a direction perpendicular to a transfer direction of the banknotes with the transfer path for transferring the banknotes interposed therebetween, and periodicity of a reception signal detected by the ultrasonic wave receiver is determined to detect whether a zero sheet, a single sheet or double sheets of the banknotes pass through the transfer path according to generation or not of the periodic signal and/or a frequency of the generation, whereby utilization of space of an automatic teller machine can be enhanced by reducing volume of the apparatus through the vertical arrangement of the ultrasonic wave generator and the ultrasonic wave receiver, and, at the same time, double sheets of the banknotes can be detected by effectively detecting the number of sheets of banknotes, and efficiency of processing the banknotes can be enhanced.
2. Description of the Related Art
Generally, in an automatic teller machine, an apparatus for detecting double sheets of banknotes is provided on a transfer path for transferring the banknotes and detects whether or not the banknotes transferred one by one along the transfer path are overlapped with each other and transferred in double sheets.
At this point, an ultrasonic sensor is chiefly used in the apparatus for detecting double sheets of banknotes described above. In configuring such an ultrasonic sensor for detecting double sheets, generally, an ultrasonic wave generator and an ultrasonic wave receiver are provided over and under the transfer path, respectively, so that the ultrasonic wave generated by the ultrasonic wave generator passes through the transfer path and is then detected by the ultrasonic wave receiver to detect double sheets of the banknotes passing through the transfer path.
However, as described above, when double sheets of banknotes passing through the transfer path are detected using the ultrasonic sensor, there is a problem in that a reflective wave reflected by the banknotes transferred between the ultrasonic wave generator and the ultrasonic wave receiver or reflected by the ultrasonic wave generator and the ultrasonic wave receiver enters the ultrasonic wave receiver and thus a reception signal is distorted. Therefore, in configuring an ultrasonic sensor for detecting double sheets in an automatic teller machine, as shown in Korean Patent No. 10-1276492 (issue date: Jun. 12, 2013) entitled “Bill detecting apparatus using ultrasonic sensor and detecting method thereof,” an ultrasonic wave generator 10 and an ultrasonic wave receiver 20 are provided over and under a transfer path through which a banknote 11 passes, respectively, in which the ultrasonic wave generator 10 and the ultrasonic wave receiver 20 are provided to face each other in a diagonal direction with respect to the transfer path so that the effect of the reflective wave can be minimized by allowing an ultrasonic wave transmitted from the ultrasonic wave generator 10 to be received by the ultrasonic wave receiver 20 in the diagonal direction at a predetermined slope.
However, since in the above-described conventional ultrasonic sensor, as shown in FIG. 1, the ultrasonic wave generator and the ultrasonic wave receiver are respectively arranged over and under the transfer path to face each other in a diagonal direction at a predetermined slope with respect to the transfer path, the installation space of the ultrasonic wave generator and the ultrasonic wave receiver is expanded and thus overall volume of the apparatus increases, thereby lowering utilization of the space.